Ethylene oxidation on silver powder: A tap reactor study

Abstract The oxidation of ethylene over silver powder catalysts was studied between 475 and 575 K at pressures of circa 10 Torr under transient conditions that allowed reactions of atomic and molecular oxygen to be distinguished. Dioxygen and d 4 -ethylene were pulsed separately over silver powder in a microreactor with pulse durations of 200 μs, and the products were detected by a multiplexed mass spectrometer. This method, denoted as temporal analysis of products, allows either simultaneous pulsing of the reactants or pulse delays ranging from a few milliseconds to minutes. In these experiments both ethylene oxide and carbon dioxide were detected as products. Ethylene oxide formed instantaneously on the time scale of the reactant pulse, but carbon dioxide formed with a much slower time constant, characteristic of the decomposition of surface carbonate, indicating the importance of secondary interactions of CO 2 with surface oxygen in the kinetics of CO 2 formation. Pulse-probe experiments, in which the catalyst was first loaded with adsorbed atomic oxygen and then reacted with anaerobic ethylene pulses or ethylene-oxygen mixtures, showed that the adsorbed species giving rise to ethylene oxide is atomic, not molecular, oxygen.

[1]  R. A. Santen,et al.  The mechanism of ethylene epoxidation , 1986 .

[2]  E. Echigoya,et al.  Kinetic and adsorption studies on vapor-phase catalytic oxidation of olefins over silver , 1982 .

[3]  A. Bell,et al.  Infrared spectra of adsorbed species present during the oxidation of ethylene over silver , 1975 .

[4]  Charles T. Campbell,et al.  The interactions of O2, CO and CO2 with Ag(110) , 1984 .

[5]  Charles T. Campbell,et al.  Chlorine promotion of selective ethylene oxidation over Ag(110): Kinetics and mechanism , 1985 .

[6]  C. Campbell.  Chlorine promoters in selective ethylene epoxidation over Ag(111): A comparison with Ag(110) , 1986 .

[7]  M. Paffett,et al.  The adsorption of ethylene oxide on Ag(110) and Pt(111): Relevance to selective olefin oxidation , 1986 .

[8]  M. Barteau,et al.  Low-pressure oxidation mechanism and reactivity of propylene on silver(110) and relation to gas-phase acidity , 1983 .

[9]  W. Richarz,et al.  Kinetics of Ethylene Oxidation on a Supported Silver Catalyst , 1979 .

[10]  P. Biloen,et al.  Adsorption of oxygen on Ag(110) studied by high resolution ELS and TPD , 1981 .

[11]  van Ra Rutger Santen,et al.  The mechanism of ethylene epoxidation , 1981 .

[12]  H. Engelhardt,et al.  Adsorption of oxygen on silver single crystal surfaces , 1976 .

[13]  R. M. Lambert,et al.  Identification of atomic and molecular oxygen surface species on rubidium-dosed Ag(111) , 1981 .

[14]  M. Barteau,et al.  Acetylenic complex formation and displacement via acid-base reactions on Ag(110) , 1982 .

[15]  P. Biloen,et al.  Interaction of O2, CO2, CO, C2H4 and C2H4O with Ag(110) , 1983 .

[16]  M. Bowker,et al.  Oxygen induced adsorption and reaction of H2, H2O, CO and CO2 on single crystal Ag(110) , 1980 .

[17]  R. M. Lambert,et al.  Basic studies of the oxygen chemistry of silver: Oxygen, dioxygen and superoxide on potassium-dosed Ag(100) , 1981 .

[18]  C. Campbell.  The selective epoxidation of ethylene catalyzed by Ag(111): A comparison with Ag(110) , 1985 .

[19]  Van Santen,et al.  Reactivity of oxygen adsorbed on silver powder in the epoxidation of ethylene , 1981 .

[20]  M. Barteau,et al.  The adsorption of molecular oxygen species on Ag(110) , 1980 .

[21]  Robert B. Grant,et al.  A single crystal study of the silver-catalysed selective oxidation and total oxidation of ethylene , 1985 .

[22]  Haruo Kobayashi,et al.  Studies on the catalytic oxidation of ethylene by means of the pulse technique , 1970 .

[23]  A. Czanderna,et al.  Thermal desorption mass spectrometry of oxygen chemisorbed on thermally etched and polycrystalline silver filaments , 1975 .

[24]  A. Bell,et al.  The relationship of adsorbed species observed by infrared spectroscopy to the mechanism of ethylene oxidation over silver , 1975 .

[25]  Charles T. Campbell,et al.  Model studies of ethylene epoxidation catalyzed by the Ag(110) surface , 1984 .

[26]  T. Seiyama,et al.  Isotopic study of the temperature-programmed desorption of oxygen from silver , 1982 .

[27]  Charles T. Campbell,et al.  Atomic and molecular oxygen adsorption on Ag(111) , 1985 .

[28]  R. F. Pottie,et al.  Mass spectra of some deuterated ethanes. I. The effect of ionizing voltage , 1968 .

[29]  The effect of electrochemical oxygen pumping on the rate and selectivity of ethylene oxidation on polycrystalline silver , 1981 .

[30]  G. Neubauer,et al.  Kinetic studies on the mechanism of the catalytic ethene oxidation , 1987 .